On Tuesday, the New York Times reported that new intelligence reviewed by US officials suggested that a pro-Ukrainian group had carried out the attack on the Nord Stream pipelines.

Citing anonymous US officials, the report said there was no evidence that Ukrainian President Volodymyr Zelensky or his top lieutenants were involved in the operation.

The US newspaper reported that the officials declined to disclose the nature of the intelligence, how it was obtained or "any details of the strength of the evidence it contains".

It added: "Officials who have reviewed the intelligence said they believed the saboteurs were most likely Ukrainian or Russian nationals, or some combination of the two."

Responding to the New York Times report, Mr Podolyak added that Kyiv had no information about what had happened.

Also on Tuesday, German newspaper Die Zeit reported that German authorities had made a breakthrough in their investigation into the cause of the attacks.

According to joint research published by the paper and other German media organisations, the boat used to plant the explosives was a yacht hired from a firm based in Poland, which reportedly belonged to two Ukrainians. The nationalities of those who carried out the attack were unclear.

Germany's public prosecutor declined to comment on the report but Defence Minister Boris Pistorius warned against jumping to conclusions. It could be a false-flag operation aimed at pinning the blame on pro-Ukrainian groups, he told German radio: "The likelihood of one [theory] or the other is just as high."

At least 50m (164ft) of the underwater Nord Stream 1 pipeline bringing Russian gas to Germany is thought to have been destroyed by September's blast.

Danish police believe "powerful explosions" blew four holes in the pipe and its newer twin, Nord Stream 2.

German, Danish and Swedish authorities have all been investigating the incident.

Mr Peskov said Nord Stream shareholder countries should insist on an urgent, transparent investigation.

"We are still not allowed in the investigation," he said. "Only a few days ago we received notes to that effect from the Danes and Swedes. This whole thing is not just weird. It reeks of a heinous crime."

For decades, Russia supplied huge amounts of natural gas to Western Europe. But after the war in Ukraine began in February of last year, most EU countries drastically reduced their reliance on Russian energy.